A fundus camera is a camera particularly used for capturing images of inner eye and retina. Compared to other objects in photographing, the fundus does not give light itself. Light of different types projected onto an eye in a natural condition can illuminate the fundus but is not intense enough for observing the fundus or taking a picture thereof. Besides, light tends to reflect from the cornea to interfere with the observation of the fundus.
Therefore, the fundus camera must include an illuminating system capable of illuminating the fundus with a considerably intense light as well as an observing and imaging system that is free from any influence of the intense reflected light from the cornea on a film. Further, to distinguish the position of the macular or the optic disc from other areas in the captured eye image, fixation points are provided in the fundus camera, so that an examinee can turn his or her eye to a particular angle by gazing on some specific fixation point.
Please refer to FIG. 1. The gaze fixation system adopted by the conventional fundus camera mainly includes a liquid crystal display (LCD) 101, on which lightened spots 102 are provided at different positions. In using the LCD gaze fixation system, an examinee is caused to turn his or her eye and gaze on the lightened spots 102 on the LCD 101. Please refer to FIG. 2. The fundus camera using the conventional LCD gaze fixation system has an optical path design generally divided into an LCD display system 10, a light source projecting system 11, an optical camera system 12, an image displaying and monitoring system 13, and a positioning optical path system 14.
The LCD display system 10 includes an LCD display 101, a condenser lens 103 and a beam splitter 104. The light source projecting system 11 includes a photographing light source 111, a condenser lens 112, a ring-shaped slit plate 113, a relay lens 114 and a perforated mirror 115. The optical camera system 12 includes an ocular lens 121, a focusing lens 122, a magnifier 123 and a film 124. The image displaying and monitoring system 13 includes a beam-bending lens 131, a field lens 132, a mirror 133, a relay lens 134, a converter tube 135 and a monitor 136. The positioning optical path system 14 includes a semi-lens 141, a relay lens 142, a mirror 143, a light guide 144 and a light source 145.
Since the above optical path systems are independent from one another, they respectively require an independent optical path space. As a result, the fundus camera requires increased manufacturing cost. Further, the LCD for aiding gaze fixation does not include any optical path design related to a split image focusing screen. Therefore, an examiner could not quickly and precisely focus the image in the process of image focusing adjustment for individual eye diopter. However, the addition of a split image focusing system to the LCD display system would inevitably involve in the complicated problem of coordination with other optical path systems.
In view that there are still many improvements that must be made to the conventional fundus camera adopting the LCD for aiding in gaze fixation, it is tried by the inventor to develop an improved fundus examination device capable of aiding in gaze-fixation and image focusing.